Field of the Invention
The invention concerns a method to optimize a magnetic resonance sequence of a magnetic resonance apparatus that operates according to such an optimized sequence, a method to operate a magnetic resonance apparatus with such an optimized sequence, a sequence optimization unit to provide such an optimized sequence, a magnetic resonance apparatus that operates according to such an optimized sequence, and a non-transitory, computer-readable storage medium encoded with programming instructions that, when executed by a computer, produce such an optimized sequence.
Description of the Prior Art
In a magnetic resonance apparatus (also called a magnetic resonance tomography system), the body of an examination subject (in particular a patient) that is to be examined is typically exposed to a relatively high basic magnetic field, for example of 1, 5, 3 or 7 Tesla, generated by a basic magnet. A magnetic field gradient is additionally applied by the operation of a gradient control unit. Radio-frequency pulses (excitation signals) are then emitted via a radio-frequency antenna unit, which causes the nuclear spins of specific atoms in the subject that are excited to resonance by these radio-frequency pulses, to be deflected (flipped) relative to the magnetic field lines of the basic magnetic field. Upon relaxation of the nuclear spins, radio-frequency signals (known as magnetic resonance signals) are radiated that are received by suitable radio-frequency antennas and then are processed further. The desired image data are reconstructed from the raw data acquired in such a manner.
For a defined measurement, a defined magnetic resonance sequence (also called a pulse sequence) is to be emitted that is composed of a series of radio-frequency pulses (in particular excitation pulses and refocusing pulses as well as gradient pulses in coordination therewith that are activated) in different spatial directions. Readout windows must be set to match these chronologically. The readout windows predetermine the time periods in which the induced magnetic resonance signals are received. The timing within the magnetic resonance sequence, i.e. at which time intervals which gradient pulses follow one another, is significant to the imaging. A number of the control parameters are normally defined in what is known as a measurement protocol, which is created in advance and retrieved (from a memory, for example) for a specific measurement, and can possibly be modified on site by the operator who can provide additional control parameters—for example a specific slice interval of a stack that of slices to be measured, a slice thickness etc. A magnetic resonance sequence is then calculated on the basis of all of these control parameters.